The field of the invention generally relates to automatic washing machines, and more particularly relates to unbalanced load and lid switch controls for such washing machines.
As is well known, a typical top-loading automatic washing machine has a lid switch that is connected in series with the motor to prevent the motor from being energized when the lid is open. The lid switch provides an interlock safety feature wherein access to the clothes basket is prevented during agitation and high speed spin. A typical top-loading automatic washing machine also has an unbalanced load switch that de-energizes the motor during high speed spin if the lateral excursion of the outer tub reaches a point where the tub trips the unbalanced load switch. The unbalanced load switch functions to prevent damage to the washing machine when the clothes load is not adequately balanced. Washing machines that use a separate switch for the lid switch function and the unbalanced load function have the added cost of a second switch and associated mounting apparatus.
Some prior art devices have used a single switch to provide the functions of both a lid switch and an unbalanced load switch. In one approach, the switch is mounted to a bracket that is positioned underneath the top panel of the cabinet. The lid has a downwardly extending prong that is aligned to insert through a small aperture near the front of the lid recess. In the closed lid position, the prong pushes against a biased lever that pushes up against the downwardly extending plunger of the switch. With this arrangement, the lid switch function can be overridden by inserting a screwdriver or other similar tool through the aperture to push the lever down while the lid is open. Overriding the lid switch function enables a maintenance technician to perform certain diagnostic testing, but the insertion of a tool through the aperture may chip the enamel resulting in rusting around the aperture. Another drawback of the device is that the switch bracket mounts between horizontal inwardly directed underside flanges of the top panel at the side and front. These flanges may not always be precisely aligned due to production tolerances and, as a result, factory and/or field adjustments may be necessary to make the switch function properly. Such adjustments are expensive.
In another prior art device using a single switch for combined functions, a horizontal piston actuator with a forward bias extends into the lid recess from a cylinder mounted behind the rear wall of the recess. When the lid is closed, the rear of the lid pushes the piston rearwardly. The piston is coupled to an arm that pushes against the plunger of the switch. The arm also has a downward extension or paddle that can be pushed forward by a tab on the tub to activate the unbalanced load function. Such arrangement has a drawback in that a quarter or other similar object can be positioned between the lid and the piston within the lid recess to permanently override the lid switch function. This action could result in unsafe operations such as spinning with the lid open. Also, the coin or other similar object could wear or chip the enamel on the lid.